EXTREME EVENTS AFFECTING WATER RESOURCES IN THE HOPE RIVER WATERSHED IN JAMAICA: USE OF WETSPRO FOR BASEFLOW SEPARATION AND ITS LONG TERM TREND

The Hope River watershed in Jamaica is one of the major watersheds relying on rainfall for its source of water feeding the Hope River and its tributaries. The Hope River is one of the major sources of surface water for the Kingston basin of Jamaica, housing the capital city of Kingston The Kingston basin is the smallest but the most densely populated basins of Jamaica, the third largest island in the Caribbean. The basin comprises of the alluvial plains of the Ligueanea aquifer and the volcanics and volcanoclastic rocks of the Hope River watershed. Contamination of the of the Ligueanea aquifer has restricted the supply of potable water to the Hope River thus relying on rainfall alone. Seasonal and decadal variations in the daily streamflow of the Hope River has shown significant variability which were prominent during periods of drought (2009-2010, 2014 and 2015) and periods of extreme rainfall from hurricanes and storms. Long term sustainability of the water resources demands a detail analysis of the baseflow in the river and variation in groundwater levels as well as overall pattern of sub-surface flow. This paper deals with an holistic study of the hydrology and hydrogeology of the Kingston basin with special emphasis on the baseflow separation, its trend and the overall spatial and temporal fluctuation of groundwater flow. The paper shows the application of 3 tools for baseflow separation ie WETSPRO, N and M method and the Echardt method of baseflow separation. Years of drought and floods are isolated and correlated with rainfall pattern. GIS based mapping was used to show the slope and direction of flow for groundwater and impact of drought on sub-surface flow. Results showed that WETSPRO is a strong tool for specific water engineering purposes, such as baseflow separation, and can also complement other approaches to improve performance. It is also seen that drought does not have significant impact on the groundwater flow but impacts the flow in the river and its intake to the reservoir for supply.